1. Field of the Invention
The present invention is directed to the manufacturing of veneer and, more particularly, to a reciprocating lengthwise veneer slicing apparatus and a method of its use.
2. Description of Related Art
Manufacturing veneer from logs is well-known. In general, veneer is either cut from logs using a vertical slicer or peeled from logs using a lathe. Typical vertical slicers cut the veneer cross-wise from the log, or against the grain. Typical lathe peelers cut the veneer from a rotating log.
Traditionally veneer has been produced by preparing trunks of various species of trees for a slicing operation in which thin sheets of veneer are produced which can later be made into articles of furniture or decorative wall paneling. Preparation involves shaping the tree trunk to a desired configuration and size to form a flitch. The shaping is usually performed by longitudinally sawing the trunk to give it a generally rectangular or semi-circular cross-sectional configuration.
After the flitch has been shaped, it is cooked in a vat of hot water, for example, 190° F., for a period of time sufficient to condition it for the slicing operation, that is, until the interior of the flitch has reached a desired temperature. The cooking operation conditions (i.e., heats) the flitch so that it will not splinter, split, or tear during slicing and improves surface smoothness and ease of cutting. The cooking time varies according to the specie of wood, but is generally 24–48 hours. Once a flitch reaches the proper temperature, the flitch is removed from the water bath and transported to the veneer slicer.
The vats of hot water are generally several feet deep to accommodate several flitches at a time. This creates a danger in that a person may fall into the vat of hot water. The vats also present sanitary/sewage issues regarding the maintenance and disposal of dirty and extractive contaminated water.
Veneer slicers come in many forms and traditionally work by reciprocating the flitch vertically against the blade as the blade moves forward or upward into the flitch. A reciprocating veneer slicer typically has a reciprocating flitch table and a blade and nosebar carriage. The flitch table holds the flitch and reciprocates generally in a vertical plane. During reciprocation, the flitch is passed over the blade to cut a slice of veneer and then returns to its initial position.
The blade and nosebar carriage is incrementally advanced toward the flitch table so that veneer slices of uniform thickness are cut from the flitch during each cutting stroke. In order to return the flitch and flitch table to their initial position without interfering with the blade and nosebar, conventional systems have utilized means for tilting the blade and nosebar back away from the flitch table to insure that the flitch and flitch table clear the blade and nosebar during the return stroke. A gap is provided between the nosebar and the blade through which a veneer sheet passes as it is sliced from the flitch.
Conventional systems have normally utilized feed screws for advancing the blade and nosebar carriage toward the flitch table. Typically, the blade and nosebar carriage is advanced an incremental distance toward the flitch table during each rotation or portion of a rotation of the feed screw. Generally, a mechanical means is provided so that the blade and nosebar carriage is advanced the incremental distance during a very small portion of the rotation and is then held stationary by the mechanical means during the rest of the rotation. It is during this dwell that a sheet of veneer is sliced. A disadvantage of such systems is that the thickness of the veneer slice is determined by the mechanical movement limiting means, specifically, by the increment of advance of the feed screw which moves the carriage. Therefore, the slice thickness is difficult to vary.
In some slicers, a control system is provided for advancing and retracting the blade and nosebar carriage. This system replaces the feed screw and permits the blade and nosebar tilt mechanism to be eliminated. The control system includes a linear actuator for incrementally advancing and retracting the carriage and a programmable linear motion controller for controlling the sequence in which the linear actuator advances and retracts the carriage and the distance in which the linear actuator advances and retracts the carriage. This method does allow for more rapid change in thickness than the feed screw.
The flitch is conventionally held against a flat surface of the flitch table by mechanical clamps, commonly called “dogs”. This entire assembly is moved in the vertically reciprocating motion. Using dogs to hold the flitch in place results in wasted material, since the thickness of the flitch between the flat holding surface and the top of the dog cannot be sliced by the blade. The remaining material, commonly called a “backing board”, is often approximately 20 millimeters in thickness. Thus, the conventional dog clamping systems result in considerable waste of material.
Another problem caused by using dogs to hold the flitch in place is that uneven pressure exerted by the dogs, coupled with the reduced strength of the flitch as material is cut away, can cause the flitch itself to bend or curl during the latter slicing stages. This results in an inferior product and wasted material.
As the flitch is sliced into veneer sheets, the blade becomes dull. Eventually, the machine operator will need to rotate the blade about the pivot axis to adjust the angle of attack to maintain an improved cutting edge presented to the flitch or replace the blade. To facilitate adjusting the angle of attack, a pair of adjusting screws is coupled to the carriage and to the blade. By turning the screws, the blade is lifted relative to the carriage to rotate the blade about the pivot axis. As the blade rotates about the pivot axis, the angle of attack of the blade changes relative to the flitch.
Another adjustment that must be performed prior to initiation of a slicing operation is to position the nosebar with respect to the edge of the blade. The nosebar provides support for the veneer sheet as it is being sliced. In order to produce a high-quality sheet of uniform thickness, the nosebar must be accurately positioned with respect to the cutting edge of the blade.
Conventionally, the nosebar is mounted to a nosebar support means which, in turn, has a large feed screw at each end thereof. Adjustment of the horizontal position of the plate is accomplished by manually rotating the two screws, causing the ends of the nosebar support means and the nosebar mounted thereto to move forward or backward. An operator moves back and forth from one side of the apparatus to the other, checking the alignment of the nosebar and the blade edge by hand upon each rotation of the screws until satisfied that the nosebar and the blade edge are properly positioned relative to one another across the entire length of the blade (commonly 13–17 feet). In this system, it is difficult to move the nosebar by the very small and precise amounts needed for accurate positioning. Thus, the procedure tends to be somewhat time-consuming and requires an operator of substantial skill.
The rapid oscillation of the nosebar and blade places a substantial strain on the equipment. It is frequently necessary to adjust the settings of the blade and nosebar. Also, it is necessary to change the settings when changing from one flitch to another, particularly, if the flitches are of different woods or at significantly different temperatures. Additionally, during the operation of the apparatus, it often becomes necessary to stop the system for one reason or another. For example, the apparatus might jam, a flitch might fall off of the flitch table, or the flitch may have a nail or other foreign object embedded therein, which must be removed to avoid damaging the blade. In such circumstances, the apparatus must be stopped, and the carriage must be moved away from the flitch table for servicing. After servicing is completed, the carriage must be returned to the correct position to continue the slicing operation. This is a relatively time-consuming operation which significantly increases the downtime of the apparatus.
In a longitudinal lumber slicing apparatus, prepared logs are queued on a conveyor system. One-by-one, the logs pass over a blade and return to the conveyor system. Thus, one slice of veneer is cut from each log before another slice is cut from any log. Maintaining the sequence of the veneer cut from each log becomes complicated.